Tyuya-Muyun Cave, Kirghistan
Speleothems: small (up to 15 cm), gray-black stalactites tabular crystals in crusts
Frequency: Rare
First description of cave occurrence: Smolianinova, N.N. 1970. Some data on mineralogy and geochemistry of the Tyuya-Muyun ore deposit. in Geology and geochemistry of ore deposits, Nauka, Moscow: 56-90 (in Russian)
Other cave locations & References: Zolushka Cave, Bukovina, Ukraine - Andreichock, V. (pers. comm.) in Hill, C.S. & Forti, P. 1997. Cave Minerals of the World (2nd. ed.). National Speleological Society, Huntsville AL, 464pp
limestone (the massif is surrounded by Silurian black schists and sandstones, and it is impregnated by ore vein)
Group: Oxides
Chemical formula: Mn4+(O,OH)2·(Co,Ni,Mg,Ca)x(OH)2x·nH2O
[According to the official IMA-CNMNC List of Mineral Names (http://nrmima.nrm.se/imalist.htm)]
Deposition and stability: Derived from manganese ore, in which some Mn has been replace by Cu, Ni and Co (Tyuya-Myuyn Cave, Kirghizstan) Formed at the redox boundary as oxidizing conditions replaced the reducing ones near the top of the water table (Zolushka Cave, Ukraine)
Color: gray-black
+ calciovolborthite (Tyuya-Muyun Cave, Kirghizstan)
Mixed with birnessite (Zolushka Cave, Ukraine)
- Hexagonal